A portable telephone system, such as the second-generation digital cordless telephony (CT2), has multiple transceivers which are located at a call point station or public base station known as a telepoint. These transceivers allow persons using portable or wireless telephones to access the public telephone network when in range or within a service area.
However, a range of distances up to about 400 feet, depending on the surroundings, is possible. This distance, while providing a convenience as to where calls can be placed from also creates two new problems. Unlike today's "corded" phone booth where the caller has to actually reach it before a call can be placed, there is no indication of an in range condition until after the caller has failed to make a call in the wireless system.
Another problem is created when the caller, who is within range of the cordless telephone booth, but cannot acquire a dial tone to obtain an open line, since the transceivers of the base station can handle only a limited number of simultaneous phone calls made by different portable telephones. Because the caller does not know if one of the transceivers is available or they are fully utilized until the caller attempts to access the transceivers, it is frustrating for the caller to find that a transceiver is not available only after a phone call has been attempted. Even if a "busy" visual annunciator was available at the telepoint, if a caller is too far away or not within the line-of-sight of the annunciator, the caller would still not receive any busy indication.
Unlike today's "corded" phone booths, the callers wait in line and psychologically are prepared to wait, since they can see their placement in the queue. However, a cordless telepoint user on the other hand, is not prepared to wait, but is frustrated instead, since there is no indication of a queue line being formed.
Therefore, a need arises for handset or cordless telephone subscribers to obtain in range and busy information from CT2 base stations before their call attempts fail. Currently, losses of revenue may occur since the quantity of calls that could not be made, due to a busy base or telepoint condition is not tracked. Hence, there is also a need for a means of determining how many call requests were attempted during a busy hour to justify system expansion.